In order to set up a communication between any two or more computer systems or similar other systems, any digitized delivery of voice, video or data has to meet the rules of the five layers of the Internet and other families of protocols. The topmost layer (layer 5) is the Application layer that represents such protocols as File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP), Telnet, and others. The next two protocol layers, layers 4 and 3, are called TCP and Internet Protocol (IP). These are used by the systems attached to the Internet and other private networks. The layer 2 is the Data Link layer protocol. The examples for the layer 2 are Ethernet, Fiber Distributed Data Network (FDDI), Frame Relay (FR) and Asynchronous Transfer Mode (ATM). Some of these layer 2 protocols transgress into other protocol layers, above and below, as dictated by the nature of transmission rules of the protocol. The bottom Physical layer (layer 1) is represented by the physical medium of transmission such as the single-mode or multi-mode fibers used for ATM, twisted copper pairs used in Local Area Networks (LANs), radio channels for Wide Area Networks (WANs), and related hardware.
The conventional mode of transmission of digitized signals, hereinafter called digital transmission or simply data to represent all forms of digital transmissions such as voice, video, text, and image, is generally datagram based. Datagram implies a preassigned set of data bits, grouped together in what is called a packet, that is transferred from one end-system to another more like postal mail delivery system. Each packet has a header that carries information about the packet such as its source system address, destination system address, its length, a methodology to check its accuracy and some other related information. For instance, the header for IP packet, which is a minimum 20 Bytes (160 bits), carries information such as version, length of the header, type of service, total length, identification (of the packet), flags (to activate certain options), fragment offset (identifying a portion of the packet if it is not the whole packet), time to live, protocol number, header checksum source IP address, destination IP address, options, and padding (of bits if necessary). All these can use up to 64 Bytes of data. The data portion of the IP packet follows the header. Any other type of frame or packet (all hereinafter referred to as packet only) has a similar bit make-up.
For smaller packets, such as in the case of ATM packets, a larger overhead of header data compared to its data content (called payload) is employed. Use of such high overhead causes congestion in the traffic channels and slows down transmissions. This is further compounded by the fact that raw data output from an end-system is encapsulated by the protocol packet from the layer below which is further encapsulated by the protocol packet from the layer still below and so on. For example, to the TCP header is added the IP header, to which is added the FR header and so on down the protocol suite to transmit an e-mail coming out of an end-system that rides on, say, an FR network.
Overheads burden transmission and network latency. The current environment of multi-protocol usage both in the LANs and WANs add an inordinate amount of header overheads to raw data, that is raw information content, thereby greatly slowing the process of transmission as well as adding to the potential for errors, traffic congestion and delay. The reasons are obvious: the bulk of bits transmitted and complex rules of individual protocols increase the barriers to a smooth traffic flow significantly. This environment is further complicated by the fact that TCP is session oriented protocol on top of the IP and other protocols which are oriented as datagram protocol. The former (TCP) establishes a virtual or logical connection between two end-systems while the latter (IP) provides real routing of packets along the most suitable path decided by the (packet) routing mechanism.
The proposed invention, comprising TCP switching, eliminates the multi-protocol complexities for the first time. The invention provides the tool for converting the conventional or classical TCP into Fast TCP resulting in the SLAP. In brief, this mechanism establishes a TCP session through TCP switching devices thereby eliminating the need for layer 2 switches, layer 3 routers and all other multiplexing or concentrator devices.